The Retirement Commissioner says increasing the age of superannuation is a "no-brainer", but the Government's adamant there's no need to do anything.

"The number of 65-plus will double in the next 25 years, the cost of super will triple in the next 20 years," Diane Maxwell told The Nation on Saturday morning.

"Our dependency ratio - the number of people of working age to retirees - will go from 4.4 to 2.4 [per working person]. We can't pretend this isn't happening."

She wants the age lifted from 65 to 67, three months a year over the course of a decade. Growing numbers of people are still working when they hit 65, and increasing life expectancy means they're drawing the pension longer than in decades past.

Prime Minister John Key says he would resign before he lifted the retirement age, and much of New Zealand agrees with him. A recent survey by the Retirement Commission found two-thirds of Kiwis want it kept at 65.

"I'm hoping to change the voters' minds," says Ms Maxwell. "If I can change the voters' minds, I can change [Mr Key's] mind."

To do that, her team's put together a series of videos intended to win the public over, rather than a written report few will read.

"This has to go out to New Zealand. This has to be understood by voters, by taxpayers. We've got to take the jargon out of it, we've got to make it sensible and compelling."

But her goal isn't just to help the Government's bottom line - she wants the estimated $1.6 billion in savings a year spent on helping those who simply can't keep doing their jobs until they're in their late 60s.

"Is it a career change? Is it retraining? What do they need? Do they need a hearing aid? What do people need throughout their 50s to take them through their 60s and 70s?"

Even if the age of retirement doesn't change, Ms Maxwell says many manual jobs are probably going to disappear in the next few decades, replaced by automation, so helping people transition into other work is a win-win.

"Many of those manual jobs that broke people are dying out."

She also wants other eligibility requirements looked at, in particular how long someone has to live in New Zealand before they're eligible. Currently, it's 10 years - Ms Maxwell says the OECD average is 26.

"We do have people coming to New Zealand and we do have parents coming to New Zealand... and we need to think about, in the longer term, is this is a cost blowout? How [do] we manage that?"

Commerce Minister Paul Goldsmith says the Government has no plans to raise the age, convinced the tripled cost of Super can be covered by growing the economy and spending carefully.

"The projections are in 2045, 30 years from now, that will increase to 7 percent of GDP. The world's not going to come to an end. We can afford that," he told The Nation.

"You don't have to cut anything... If you keep good, sound control of the finances, there's no reason to think that New Zealanders can't afford to look after older people in their retirement."

As for immigrants' eligibility, Mr Goldsmith said it was "a matter for the Minister of Finance or Immigration to deal with. It's not my area."